Steel material for hardening and method for producing the same

Abstract

The present invention provides a steel material for hardening, including chemical components, by mass %, of: C: 0.15 to 0.60%; Si: 0.01 to 1.5%; Mn: 0.05 to 2.5%; P: 0.005 to 0.20%; S: 0.001 to 0.35%; Al: over 0.06 to 0.3%; and total N: 0.006 to 0.03%, with a balance including Fe and inevitable impurities including B of not more than 0.0004%, in which a hardness R at a position 5 mm away from a quenching end measured through a Jominy-type end-quenching method specified in JIS G 0561, and a calculation hardness H at a position 4.763 mm away from the quenching end satisfy the following Equation (1).H×0.948≦R≦H×1.05  Equation (1)

Description

TECHNICAL FIELD[0001]The present invention relates to a steel material for hardening having excellent machinability and hardening stability, and a method for producing the steel material.[0002]The present application claims priority based on Japanese Patent Application No. 2010-124536 filed in Japan on May 31, 2010, the contents of which are incorporated herein by reference.BACKGROUND ART[0003]In recent years, steels have become increasingly stronger, but this causes a problem of deterioration in workability. Thus, there is a strong demand for steels having improved machinability while maintaining the strength. Conventionally, in order to improve the machinability of the steel, elements such as S, Pb, and Bi have been added for improving the machinability. Pb and Bi improve the machinability and have a relatively small effect on the forging, but deteriorate properties related to strength such as impact properties.[0004]Further, the element S forms a soft inclusion such as MnS under ...

AI Technical Summary

Benefits of technology

[0028]According to the present invention, the effect of improving the machinability prolongs the tool life, thereby reducing the production cost. Further, the stable hardenability is achieved, thereby suppressing the variations in the deformation caused by the heat treatment.

Problems solved by technology

In recent years, steels have become increasingly stronger, but this causes a problem of deterioration in workability.

In particular, when MnS is stretched through forging or rolling, this causes anisotropy in impact properties and the like, and mechanical properties become significantly weak in a specific direction.

As described above, even if elements effective in improving the machinability are added, the impact properties deteriorate, and hence, it is difficult to achieve both the strength and the machinability at the same time.